Printer ink reservoir



FIG. 1 is a left-front perspective view of a printer ink reservoir showing the new design;

FIG. 2 is a top view thereof;

FIG. 3 is a left side view thereof (a right side view is not shown but is a mirror image of the left side view);

FIG. 4 is a front view thereof; and,

FIG. 5 is a bottom view thereof.

The broken lines in FIGS. 1-5 are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a printer ink reservoir, as shown and described. 